K.B.
My four year old daughter is very similar in temperment to your son. She is an agressive, fearless, rough-and-tumble girl (instead of walking up to her friends to give them a hug, she'll race up and give a huge hug, half the time knocking both herself and the friend over in the process) who loves to be right in the middle of everything.
I've found that giving her time frames and getting enough exercise make a huge difference with her.
For time frames, you say you have " x " number of minutes to finish what you are doing. (Playing, eating, bathtub, etc.) Set a timer, so it can be the "bad guy", then FOLLOW THROUGH. Don't get into the "one more minute" trap. Just say "those are the timer's rules". I've found that this grounds my daughter because she knows exactly what is going on and when, without me suddenly deciding that what she has been doing has gone on long enough.
Getting her enough exercise is really important too - whether going on a snail-hunting expedition or "treasure" hunt around the neighborhood.
With a tiny bit of planning ahead, you can spray paint and hide various small things in his favorite color for your treasure hunt. Even if it's just a few leaves and rocks that you paint, and you put them right out in the open to "hide" them, they really get a kick out of the novel color.
For those days when you're really tired, find a children's music/dance video and encourage him to do wild dancing to it. (Don't do this too close to bed time, as it gets kids pretty wound up.)
A book that helped me is "The Happiest Toddler on the Block" by Harvey Karp. It had some really good pointers.
Yes, boys and girls are different, but be very careful not to stereotype them, though. My daughter has always had full choice of dolls, tea sets, dress up clothes and her barbie dream house, and some quiet friends to play with those toys. Most of the time, though, she decides she wants to be outdoors hunting snails and bugs, climbing trees, and driving cars and trains through mud puddles with the more rambuctious of her friends.